1. Field of the Invention
This invention relates to a device for detecting camera motion during the photographing operation of a camera and for giving a warning as necessary.
2. Description of the Prior Art
The cameras designed for general use by people these days have almost every necessary function thereof automated, including such devices as an automatic focusing device, an automatic film winding and rewinding device, an automatic exposure device, an automatic light adjustment device, etc. These automatic devices aim at improving the quality of pictures. Despite these devices, however, a blurred picture would result if the photographer moves or the camera moves due to the operation of an internal device such as a return mirror, a shutter drive mechanism or the like. The conventional still picture cameras have been provided with some device that displays a warning against camera shake in the event of photographing at a shutter speed lower than a certain given speed. However, this is nothing more than a mere mechanical warning and does not permit confirmation of an actual camera shake. Furthermore, this conventional camera shake warning device has been incapable of giving any warning in the event of actual camera shake occurring in photographing at a relatively high shutter speed.
A camera shake detecting device has been known from the disclosure made in Japanese Laid-Open Patent Application No. SHO 58-70217. This prior art device is arranged as shown in FIGS. 1A and 1B of the accompanying drawings. The device comprises acceleration detecting means which is arranged to detect acceleration and to generate an electrical signal representing the degree of the acceleration; warning display means for displaying a warning; a warning circuit which is responsive to the opening and closing operation of a shutter of the camera and is arranged to energize the warning display means when the above-stated electrical signal exceeds a threshould value, so that a warning can be displayed indicating that a photography image has blurred. This device necessitates use of an acceleration detector 10. The detector 10 is preferably a micro-mechanical acceleration detector which is formed in one unified body with an integrated circuit of a metal-oxide semiconductor (MOS) as shown in FIG. 1B. The micro-mechanical acceleration detector is prepared in the following manner: An n-type silicon (n-Si) substrate 100 has a P.sup.+ area 101 formed by partly doping it with boron (B). Over this n-Si substrate is formed an epitaxial layer 102. The epitaxial layer 102 is provided with a shallow gate shaped etched void space 104. A cantilever 110, which consists of a silicon dioxide (SiO.sub.2) layer 106 and a Cr-Au layer 108, extends over the void space 104. When the whole detector 10 vibrates, a distance between the cantilever 110 and the P.sup.+ layer 101 varies. This variation is taken out from electrodes 12 and 14 as a change in electrostatic capacity.
The cameras of today, as mentioned above, have versatile functions, which are sequentially controlled by a microcomputer consisting of integrated circuits. Accordingly, a camera shake detecting device must be compatible with these circuits. Otherwise, circuit arrangement becomes difficult. For example, if a camera is provided with such a blur detecting element and a blur control circuit that are incompatible with the conventional circuits, the camera must have a complex arrangement of electrical circuits and components.
It is a first object of this invention to provide a blur detecting device which is compatible with circuits conventionally arranged for a camera.
It is a second object of this invention to provide a blur detecting device including a sensor and an optical system which are usable also as a sensor and an optical system for an automatic focusing (AF) device.
A blur detecting device according to this invention is arranged to use a charge coupled device (CCD) which has been developed by the prior art for automatic focusing and to produce a blur detection signal on the basis of an image signal obtained from the CCD.
The term "camera shake", as used herein for the purpose of this invention, means shaking or vibration of the camera resulting in a blur of the image of an object to be photographed due to movement of the camera caused, for example, by the vibration of a hand holding the camera and also by the vibration of the internal mechanism of the camera.
It is a third object of this invention to provide a blur detecting device wherein an image signal of a CCD which is obtained by converting an image of the object to be photographed into an electrical signal is processed under a control performed based on photographing conditions, such as film sensitivity information (ISO) and set shutter speed information (TV) or set aperture value information (AV); and the device gives a blur detection signal which is adjusted to these photographing conditions.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.